Tyler Joseph has to get Tik Tok because his band mate Josh Dun has it, so if both of them have it then it would make the Clique more happy, the Tik Tok For You page more entertaining, and most likely we would see more of Rosie because he would probably put her in his videos. If he makes more vids of Rosie then everyone will be smiling more. Also lots of people want Tyler to do tik tok dances.